/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution
{
public:
    ListNode *reverseList(ListNode *head)
    {
        ListNode *reversedHead = nullptr;
        ListNode *nextPick = head;
        while (nextPick != nullptr)
        {
            ListNode *picked = nextPick;
            nextPick = nextPick->next;
            picked->next = reversedHead;
            reversedHead = picked;
        }
        return reversedHead;
    }
};